09内訳が見えると下がって収まる下部の決済バー

<main class="stage">
  <section class="co is-demo" id="co" aria-label="注文書と下部の決済バー">
    <div class="co__view" id="co-view" tabindex="0" role="region" aria-label="注文書">
      <div class="co__pad">
        <p class="co__title">注文書</p>

        <div class="co__item">
          <span class="co__thumb" aria-hidden="true"></span>
          <span class="co__name">マグカップ 2個</span>
          <span class="co__price">24,000ウォン</span>
        </div>
        <div class="co__item">
          <span class="co__thumb" aria-hidden="true"></span>
          <span class="co__name">Tシャツ 1枚</span>
          <span class="co__price">19,000ウォン</span>
        </div>
        <div class="co__item">
          <span class="co__thumb" aria-hidden="true"></span>
          <span class="co__name">エコバッグ 1個</span>
          <span class="co__price">9,000ウォン</span>
        </div>
        <div class="co__item">
          <span class="co__thumb" aria-hidden="true"></span>
          <span class="co__name">靴下 3足</span>
          <span class="co__price">6,000ウォン</span>
        </div>

        <div class="co__sum" id="co-sum">
          <p class="co__sumHead">
            <span class="co__ic" aria-hidden="true"><svg viewBox="0 0 256 256" fill="currentColor"><path d="M224,56V208l-32-16-32,16-32-16L96,208,64,192,32,208V56a8,8,0,0,1,8-8H216A8,8,0,0,1,224,56Z" opacity="0.2"/><path d="M72,104a8,8,0,0,1,8-8h96a8,8,0,0,1,0,16H80A8,8,0,0,1,72,104Zm8,40h96a8,8,0,0,0,0-16H80a8,8,0,0,0,0,16ZM232,56V208a8,8,0,0,1-11.58,7.15L192,200.94l-28.42,14.21a8,8,0,0,1-7.16,0L128,200.94,99.58,215.15a8,8,0,0,1-7.16,0L64,200.94,35.58,215.15A8,8,0,0,1,24,208V56A16,16,0,0,1,40,40H216A16,16,0,0,1,232,56Zm-16,0H40V195.06l20.42-10.22a8,8,0,0,1,7.16,0L96,199.06l28.42-14.22a8,8,0,0,1,7.16,0L160,199.06l28.42-14.22a8,8,0,0,1,7.16,0L216,195.06Z"/></svg></span>
            注文の内訳
          </p>
          <p class="co__row"><span>商品金額</span><span>58,000ウォン</span></p>
          <p class="co__row"><span>送料</span><span>3,000ウォン</span></p>
          <p class="co__row co__row--total"><span>お支払い合計</span><span>61,000ウォン</span></p>
        </div>
      </div>
    </div>

    <div class="co__bar" id="co-bar">
      <span class="co__barTotal">61,000ウォン</span>
      <button class="co__pay" type="button">
        <span class="co__ic" aria-hidden="true"><svg viewBox="0 0 256 256" fill="currentColor"><path d="M232,96v96a8,8,0,0,1-8,8H32a8,8,0,0,1-8-8V96Z" opacity="0.2"/><path d="M224,48H32A16,16,0,0,0,16,64V192a16,16,0,0,0,16,16H224a16,16,0,0,0,16-16V64A16,16,0,0,0,224,48Zm0,16V88H32V64Zm0,128H32V104H224v88Zm-16-24a8,8,0,0,1-8,8H168a8,8,0,0,1,0-16h32A8,8,0,0,1,208,168Zm-64,0a8,8,0,0,1-8,8H120a8,8,0,0,1,0-16h16A8,8,0,0,1,144,168Z"/></svg></span>
        支払う
      </button>
    </div>
  </section>
</main>

@use "../../../../site/static/demo-tokens" as *;

// 주문 요약이 시야에 들어오면 하단 결제 바가 translateY 로 내려가 자리를 비운다.
// 바는 스크롤 상자 밖에 position: absolute 로 겹쳐 둔다 — 스크롤이 0 인 첫 장면에서도
// 제자리에 서 있어야 하고, 상자 안에 넣으면 내용과 함께 흘러가 버린다.
$duration: $dur-loop;
$easing: $ease-spring;
$color: $subject-blue;

@include stage($stage-ink);

.co {
  position: relative;
  box-sizing: border-box;
  width: min(300px, 92vw);
  border-radius: $r-card;
  background: $subject-cream;
  color: $subject-ink;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  overflow: hidden;
}
.co * { box-sizing: border-box; }

.co__view {
  height: 168px;
  overflow-y: auto;
  scrollbar-width: none;
  &::-webkit-scrollbar { display: none; }
  &:focus-visible { outline: 2px solid $color; outline-offset: -4px; }
}
.co__pad {
  display: grid;
  gap: $sp-2;
  // 아래 여백은 얇게 — 끝까지 내려가면 바는 이미 물러나 있으므로, 바 높이만큼 비워 두면
  // 마지막 장면이 요약 카드 아래의 빈 크림색 띠가 된다
  padding: $sp-3 $sp-3 $sp-4;
}

.co__title {
  margin: 0;
  font-size: 13px;
  font-weight: 700;
  line-height: 1.3;
}

.co__item {
  display: flex;
  align-items: center;
  gap: $sp-2;
}
.co__thumb {
  flex: 0 0 auto;
  width: 28px;
  height: 28px;
  border-radius: $r-sm;
  background: rgba(23, 20, 26, .1);
}
.co__name {
  flex: 1 1 auto;
  font-size: 11px;
  line-height: 1.4;
}
.co__price {
  font-size: 11px;
  font-weight: 700;
  line-height: 1.4;
}

// 요약 카드 — 바가 내려간 자리를 이 카드가 채운다 (빈 장면이 대표 이미지로 나가지 않게)
.co__sum {
  padding: $sp-3;
  border-radius: $r-control;
  background: rgba(47, 109, 246, .12);
}
.co__sumHead {
  display: flex;
  align-items: center;
  gap: $sp-1;
  margin: 0 0 $sp-2;
  font-size: 11px;
  font-weight: 700;
  line-height: 1.3;
  color: $subject-blue-deep;   // 파란 tint 카드 위 파란 글자 — 진한 파랑이라야 AA
}
.co__ic {
  display: inline-grid;
  place-items: center;
  width: 14px;
  height: 14px;
}
.co__ic svg { width: 100%; height: 100%; }
.co__row {
  display: flex;
  justify-content: space-between;
  gap: $sp-2;
  margin: 0;
  font-size: 11px;
  line-height: 1.6;
}
.co__row--total {
  margin-top: $sp-1;
  padding-top: $sp-1;
  border-top: 1px solid rgba(23, 20, 26, .16);
  font-size: 12px;
  font-weight: 700;
}

// ── 하단 결제 바 ──
.co__bar {
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0;
  display: flex;
  align-items: center;
  gap: $sp-2;
  padding: $sp-2 $sp-3;
  background: $subject-ink;
  color: $subject-cream;
  transform: translateY(0);
  transition: transform $dur-base $easing;
}
.co.is-down .co__bar { transform: translateY(110%); }
.co__barTotal {
  font-size: 13px;
  font-weight: 700;
  line-height: 1.4;
}
.co__pay {
  display: inline-flex;
  align-items: center;
  gap: $sp-1;
  margin-left: auto;
  padding: $sp-1 $sp-3;
  border: 0;
  border-radius: $r-pill;
  background: $stage-yellow;
  color: $subject-ink;
  font-family: inherit;
  font-size: 11px;
  font-weight: 700;
  line-height: 1.4;
  cursor: pointer;
  &:focus-visible { outline: 2px solid $subject-cream; outline-offset: 2px; }
}

// ── 격자 미리보기 루프 ──
// 주문서가 실제로 스크롤될 때 보이는 것과 같은 순서: 내용이 올라가 요약이 드러나면 바가 내려간다.
// 내용이 멈춘 뒤에 바를 움직여, 가장 크게 변하는 프레임(= 대표 이미지)이 늘 「바가 서 있는 주문서」 가 되게 한다
@keyframes coScroll {
  0%, 12% { transform: translateY(0); }
  40%, 70% { transform: translateY(-120px); }
  90%, 100% { transform: translateY(0); }
}
@keyframes coBar {
  0%, 44% { transform: translateY(0); }
  56%, 68% { transform: translateY(110%); }
  84%, 100% { transform: translateY(0); }
}
.co.is-demo {
  .co__pad {
    animation-name: coScroll;
    animation-duration: $duration;
    animation-timing-function: $easing;
    animation-iteration-count: infinite;
  }
  .co__bar {
    animation-name: coBar;
    animation-duration: $duration;
    animation-timing-function: $easing;
    animation-iteration-count: infinite;
  }
}

@media (max-width: 340px) {
  .co__view { height: 140px; }
  .co__pad { padding: $sp-2 $sp-2 $sp-3; }
  .co__title { font-size: 12px; }
  .co__thumb { width: 24px; height: 24px; }
  .co__sum { padding: $sp-2; }
}

@media (prefers-reduced-motion: reduce) {
  .co__bar { transition: none !important; }
  .co.is-demo .co__pad,
  .co.is-demo .co__bar { animation: none !important; transform: none !important; }
}

html, body {
  margin: 0;
  overflow: hidden;
}

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #17141a;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.co {
  position: relative;
  box-sizing: border-box;
  width: min(300px, 92vw);
  border-radius: 16px;
  background: #fff7e6;
  color: #17141a;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  overflow: hidden;
}

.co * {
  box-sizing: border-box;
}

.co__view {
  height: 168px;
  overflow-y: auto;
  scrollbar-width: none;
}
.co__view::-webkit-scrollbar {
  display: none;
}
.co__view:focus-visible {
  outline: 2px solid #2f6df6;
  outline-offset: -4px;
}

.co__pad {
  display: grid;
  gap: 8px;
  padding: 12px 12px 16px;
}

.co__title {
  margin: 0;
  font-size: 13px;
  font-weight: 700;
  line-height: 1.3;
}

.co__item {
  display: flex;
  align-items: center;
  gap: 8px;
}

.co__thumb {
  flex: 0 0 auto;
  width: 28px;
  height: 28px;
  border-radius: 8px;
  background: rgba(23, 20, 26, 0.1);
}

.co__name {
  flex: 1 1 auto;
  font-size: 11px;
  line-height: 1.4;
}

.co__price {
  font-size: 11px;
  font-weight: 700;
  line-height: 1.4;
}

.co__sum {
  padding: 12px;
  border-radius: 12px;
  background: rgba(47, 109, 246, 0.12);
}

.co__sumHead {
  display: flex;
  align-items: center;
  gap: 4px;
  margin: 0 0 8px;
  font-size: 11px;
  font-weight: 700;
  line-height: 1.3;
  color: #0a4fe8;
}

.co__ic {
  display: inline-grid;
  place-items: center;
  width: 14px;
  height: 14px;
}

.co__ic svg {
  width: 100%;
  height: 100%;
}

.co__row {
  display: flex;
  justify-content: space-between;
  gap: 8px;
  margin: 0;
  font-size: 11px;
  line-height: 1.6;
}

.co__row--total {
  margin-top: 4px;
  padding-top: 4px;
  border-top: 1px solid rgba(23, 20, 26, 0.16);
  font-size: 12px;
  font-weight: 700;
}

.co__bar {
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0;
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 8px 12px;
  background: #17141a;
  color: #fff7e6;
  transform: translateY(0);
  transition: transform 300ms cubic-bezier(0.2, 0.8, 0.2, 1);
}

.co.is-down .co__bar {
  transform: translateY(110%);
}

.co__barTotal {
  font-size: 13px;
  font-weight: 700;
  line-height: 1.4;
}

.co__pay {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  margin-left: auto;
  padding: 4px 12px;
  border: 0;
  border-radius: 999px;
  background: #ffd23f;
  color: #17141a;
  font-family: inherit;
  font-size: 11px;
  font-weight: 700;
  line-height: 1.4;
  cursor: pointer;
}
.co__pay:focus-visible {
  outline: 2px solid #fff7e6;
  outline-offset: 2px;
}

@keyframes coScroll {
  0%, 12% {
    transform: translateY(0);
  }
  40%, 70% {
    transform: translateY(-120px);
  }
  90%, 100% {
    transform: translateY(0);
  }
}
@keyframes coBar {
  0%, 44% {
    transform: translateY(0);
  }
  56%, 68% {
    transform: translateY(110%);
  }
  84%, 100% {
    transform: translateY(0);
  }
}
.co.is-demo .co__pad {
  animation-name: coScroll;
  animation-duration: 2s;
  animation-timing-function: cubic-bezier(0.2, 0.8, 0.2, 1);
  animation-iteration-count: infinite;
}
.co.is-demo .co__bar {
  animation-name: coBar;
  animation-duration: 2s;
  animation-timing-function: cubic-bezier(0.2, 0.8, 0.2, 1);
  animation-iteration-count: infinite;
}

@media (max-width: 340px) {
  .co__view {
    height: 140px;
  }
  .co__pad {
    padding: 8px 8px 12px;
  }
  .co__title {
    font-size: 12px;
  }
  .co__thumb {
    width: 24px;
    height: 24px;
  }
  .co__sum {
    padding: 8px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .co__bar {
    transition: none !important;
  }
  .co.is-demo .co__pad,
  .co.is-demo .co__bar {
    animation: none !important;
    transform: none !important;
  }
}

// 주문 요약이 시야에 들어오면 하단 결제 바가 내려가 자리를 비운다.
// 「보이는가」 는 스크롤 좌표 계산이 아니라 IntersectionObserver 가 판정한다 — root 는 注文書 스크롤 상자.
var co = document.getElementById('co');
var view = document.getElementById('co-view');
var summary = document.getElementById('co-sum');
// 관찰자는 붙자마자 한 번 알려 주므로, 미리보기 루프는 사람이 실제로 스크롤할 때만 끈다
view.addEventListener('scroll', function () {
  co.classList.remove('is-demo');
}, { passive: true });
if (window.IntersectionObserver) {
  var watcher = new IntersectionObserver(function (entries) {
    for (var i = 0; i < entries.length; i++) {
      co.classList.toggle('is-down', entries[i].isIntersecting);
    }
  }, { root: view, threshold: 0.45 });
  watcher.observe(summary);
}

import { useEffect, useRef, useState } from "react";
import type { CSSProperties } from "react";
import styles from "./CheckoutStickyTotalBar.module.scss";

export type CheckoutLine = { name: string; price: string };

export type CheckoutStickyTotalBarProps = {
  title?: string;
  lines?: CheckoutLine[];
  summaryLabel?: string;
  itemsLabel?: string;
  itemsTotal?: string;
  shippingLabel?: string;
  shippingFee?: string;
  totalLabel?: string;
  total?: string;
  payLabel?: string;
  groupLabel?: string;
  bodyLabel?: string;
  /** 격자 미리보기용 2초 자동 루프. 사람이 스크롤하면 꺼진다 */
  demo?: boolean;
  duration?: number;
  easing?: string;
  color?: string;
};

type Vars = CSSProperties & { "--duration"?: string; "--easing"?: string; "--color"?: string };
// ambient 가 얇아 DOM 요소 타입을 못 쓴다 — 관찰자에 넘길 만큼만 로컬 타입으로 선언
type Box = { scrollTop: number };

function ReceiptIcon() {
  return (
    <svg viewBox="0 0 256 256" width="1em" height="1em" fill="currentColor" aria-hidden="true"><path d="M224,56V208l-32-16-32,16-32-16L96,208,64,192,32,208V56a8,8,0,0,1,8-8H216A8,8,0,0,1,224,56Z" opacity="0.2"/><path d="M72,104a8,8,0,0,1,8-8h96a8,8,0,0,1,0,16H80A8,8,0,0,1,72,104Zm8,40h96a8,8,0,0,0,0-16H80a8,8,0,0,0,0,16ZM232,56V208a8,8,0,0,1-11.58,7.15L192,200.94l-28.42,14.21a8,8,0,0,1-7.16,0L128,200.94,99.58,215.15a8,8,0,0,1-7.16,0L64,200.94,35.58,215.15A8,8,0,0,1,24,208V56A16,16,0,0,1,40,40H216A16,16,0,0,1,232,56Zm-16,0H40V195.06l20.42-10.22a8,8,0,0,1,7.16,0L96,199.06l28.42-14.22a8,8,0,0,1,7.16,0L160,199.06l28.42-14.22a8,8,0,0,1,7.16,0L216,195.06Z"/></svg>
  );
}

function CreditCardIcon() {
  return (
    <svg viewBox="0 0 256 256" width="1em" height="1em" fill="currentColor" aria-hidden="true"><path d="M232,96v96a8,8,0,0,1-8,8H32a8,8,0,0,1-8-8V96Z" opacity="0.2"/><path d="M224,48H32A16,16,0,0,0,16,64V192a16,16,0,0,0,16,16H224a16,16,0,0,0,16-16V64A16,16,0,0,0,224,48Zm0,16V88H32V64Zm0,128H32V104H224v88Zm-16-24a8,8,0,0,1-8,8H168a8,8,0,0,1,0-16h32A8,8,0,0,1,208,168Zm-64,0a8,8,0,0,1-8,8H120a8,8,0,0,1,0-16h16A8,8,0,0,1,144,168Z"/></svg>
  );
}

export default function CheckoutStickyTotalBar({
  title = "주문서",
  lines = [
    { name: "머그컵 2개", price: "24,000원" },
    { name: "티셔츠 1벌", price: "19,000원" },
    { name: "에코백 1개", price: "9,000원" },
    { name: "양말 3켤레", price: "6,000원" },
  ],
  summaryLabel = "주문 요약",
  itemsLabel = "상품 금액",
  itemsTotal = "58,000원",
  shippingLabel = "배송비",
  shippingFee = "3,000원",
  totalLabel = "총 결제 금액",
  total = "61,000원",
  payLabel = "결제하기",
  groupLabel = "주문서와 하단 결제 바",
  bodyLabel = "주문서",
  demo = true,
  duration = 2000,
  easing = "cubic-bezier(.2,.8,.2,1)",
  color = "#2f6df6",
}: CheckoutStickyTotalBarProps) {
  const [down, setDown] = useState(false);
  const [live, setLive] = useState(demo);
  const viewRef = useRef<HTMLDivElement>(null);
  const summaryRef = useRef<HTMLDivElement>(null);

  // 「보이는가」 는 스크롤 좌표 계산이 아니라 관찰자가 판정한다 — root 는 주문서 스크롤 상자
  useEffect(() => {
    const view = viewRef.current;
    const summary = summaryRef.current;
    if (!view || !summary) return;
    const watcher = new IntersectionObserver(
      (entries) => {
        for (const entry of entries) setDown(entry.isIntersecting);
      },
      { root: view, threshold: 0.45 },
    );
    watcher.observe(summary);
    return () => watcher.disconnect();
  }, []);

  // 관찰자는 붙자마자 한 번 알려 주므로, 미리보기 루프는 사람이 실제로 스크롤할 때만 끈다
  function onScroll() {
    const view: Box | null = viewRef.current;
    if (!view) return;
    setLive(false);
  }

  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };
  const cls = [styles.co, live ? styles.isDemo : "", down ? styles.isDown : ""].filter(Boolean).join(" ");

  return (
    <section className={cls} style={vars} aria-label={groupLabel}>
      <div className={styles.view} ref={viewRef} onScroll={onScroll} tabIndex={0} role="region" aria-label={bodyLabel}>
        <div className={styles.pad}>
          <p className={styles.title}>{title}</p>

          {lines.map((line) => (
            <div className={styles.item} key={line.name}>
              <span className={styles.thumb} aria-hidden="true" />
              <span className={styles.name}>{line.name}</span>
              <span className={styles.price}>{line.price}</span>
            </div>
          ))}

          <div className={styles.sum} ref={summaryRef}>
            <p className={styles.sumHead}>
              <span className={styles.ic} aria-hidden="true"><ReceiptIcon /></span>
              {summaryLabel}
            </p>
            <p className={styles.row}><span>{itemsLabel}</span><span>{itemsTotal}</span></p>
            <p className={styles.row}><span>{shippingLabel}</span><span>{shippingFee}</span></p>
            <p className={`${styles.row} ${styles.rowTotal}`}><span>{totalLabel}</span><span>{total}</span></p>
          </div>
        </div>
      </div>

      <div className={styles.bar}>
        <span className={styles.barTotal}>{total}</span>
        <button className={styles.pay} type="button">
          <span className={styles.ic} aria-hidden="true"><CreditCardIcon /></span>
          {payLabel}
        </button>
      </div>
    </section>
  );
}